NEW MATERIAL: Compds. of formulae I and II, (where X, Y=O, S; R1, R5 = isopropyl, cyclopropyl, etc.; R2, R4=H, isopropyl, phenyl, etc.; R3=H, methyl, ethyl, C3-8 cycloalkyl, etc.), salts contg. salts of the same.

EXAMPLE: Sodium 3(R),5(S)-dihydroxy-6-[2-p-fluorophenyl-4-p-fluorophenylthio-6- isopropyl)phenoxy]hexanoate.

USE: Useful or the prophylaxis and treatment of ischemic heart disease, atherosclerosis, etc.

PROCESS: The compd. of formula I is obtd. by reacting phenol compd. of formula III with optically pure mesylate of formula IV to obtain acetonide of formula V, removing a protective group film it to obtain compd. of formula VI, hydrolyzing it to obtain compd. of formula VII, and cyclyzing it.